The barriers of Mose protect Venice but the system has negative impacts on salt marshes and on the lagoon morphology, a new study shows
The mobile floodgates of Mose, that were operated for the first time in October 2020, protect effectively the city of Venice from high-tide events but their repeated use, more and more probable in the light of the climatic changes taking place, risks making the salt marshes disappear.
A new study which involved a team of researchers of the University of Padua and Ca' Foscari University of Venice, analyzed the consequences of the gate closures on the fragile lagoon ecosystem.
The study, titled Loss of geomorphic diversity in shallow tidal embayments promoted by storm-surge barriers, was recently published in Science Advances and was led by professor Andrea D’Alpaos of the Department of Geosciences and by professor Luca Carniello of the Department of Civil, Environmental and Architectural Engineering of the University of Padua.
The results show that in the first 15 times in which the MOSE was activated, from October 2020 to January 2021, the barriers contributed to a 12% reduction in marsh deposition.
Salt marshes are able to survive thanks to the tides that deposit materials on their surface (70% of the sedimentation is concentrated during high water events) and this is why the researchers underline that it is necessary to find solutions to mitigate the negative effects on the conservation of the lagoon morphology.
These new analyzes, carried out by integrating modeling tools and field measurements, confirm and extend previous studies conducted by the same authors as part of the Venice 2021 project, such as the article published last December in Nature. The results show that at the scale of the entire lagoon, the regulation of the tides through the Mose system not only reduces the contribution of sediments on the salt marshes, but also favors the resuspension of sediments on the shallows by wind waves and the burying of large canals.
"It is clear that the defense of Venice is an indispensable issue and it is not under discussion. However, our analyzes show the negative effects of the Mose closures on the lagoon morphology. These are effects that must be contrasted with diversified interventions such as an increase in the supply of sediments of fluvial origin, the restoration and conservation of the salt marshes with nature based solutions and a better management of the closing procedures of the gates", Prof. Andrea D 'Alpaos of the Department of Geosciences said.